Holy Water: Weak, tempo loss, unplayable.
Spectral Cutlass: Why play this over Kingsbane?
Bogshaper: Can be amazing. Shaman need card draw. This can provide it. Only draws minions, which is nice, but prevents chaining draws if you lack many spells in hand. But minions are necessary in this game, and Shaman typically load more spells than minions, so tutoring the minions is pretty nice. Also can try shenanigans with malygos or (something else) where you need 1 specific minion to pull off a combo.
Deathweb Spider: Seems good, but probably unplayable right now. Warlock have enough life gain with Dark Pact and Spellstone. I don't see this in Cubelock. Maybe it replaces spellstone to add more board pressure, but doubtful, spellstone is too strong of removal and Cubelock have enough board pressure already.
Blood Witch: Zoo/Aggro card.
Duskbat: Zoo/Aggro card.
Dire Frenzy: Could see play in Aggro. Put it on Stonetusk Boar, then draw them with the Tol Vir guy. Quest Hunter is getting even stronger. Doubtful you play this in mid/control. Too slow and you rarely draw through your whole deck. Sure, would be nice to get more Highmanes with +3/+3, but it's unlikely to happen often.
Swift Messanger: Basically a Fireball that can't go face. Might be ok somewhere.
Royal Guard: Trash.
Spellshifter: Trash